The present invention relates to a method for precipitating polyphenylene ether. More specifically, the present invention relates to a method of producing polyphenylene ether which contains fine powder in a small amount and is easy to handle at the time of molding by precipitation.
As a process of producing polyphenylene ether resin, there is a process of subjecting phenol to oxidative polymerization in the presence of a copper compound and amines in a good solvent for polyphenylene ether. As a method for precipitating polyphenylene ether from a polyphenylene ether solution obtained by the above process, there is known a method in which a non-solvent for polyphenylene ether such as methanol and the like is added to the solution to precipitate particles of polyphenylene ether. The obtained particles of polyphenylene ether, however, contain fine powder in a high proportion, and consequently, there arise problems such as scattering of the powder at a post-step and defective bite from a hopper to an extruder during molding.
As a means for solving the above-mentioned problems, there is proposed a method in which a mixture of water and alcohol as the non-solvent is used (JP-B 60-23696). However, this method could not necessarily give satisfactory effect.
The present invention has been made in order to solve the above problems, and the object of the present invention is to obtain particles of polyphenylene ether which contains fine powder in a small amount and is easy to handle at the time of molding and the like.
The present inventors have made extensive studies to solve the above problems, and as a result, have found that the problems can be solved by dropping a polyphenylene ether solution at a portion which hardly undergoes shearing action by a stirring blade in a stirring vessel which has been fully stirred. Thus, the present invention has been accomplished.
That is, the present invention is to provide a method for precipitating polyphenylene ether, which comprises adding a non-solvent for polyphenylene ether to a solution of polyphenylene ether in a good solvent for polyphenylene ether to precipitate polyphenylene ether continuously in a stirring vessel equipped with a reciprocating stirrer, wherein the polyphenylene ether solution is dropped outside the working range of a stirring blade.